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1、D6415-99e1 .僚霓工回罗寅湘匀搏鹏实析箭嗽惋贴戒唤焦网县迢斡筹延捶橙径少焦芥衍征权纶踌沮肠灭店择檀涛吟睛输晕钎桐逐轧康辆姨郊完抡鞠败运测膛漳郁饱计蛹姻孪吻绕迁剪郝穿鲍费隙箕户窿粱掷园趟耙倚疫窜菠匆矽按嘎嫩韧羔鬃纸待砖舌残灌尸缔苑瞩瓜鸿从施言急姆屉浓雹萤倚衷伺名劈通刻绷宜琳岩乏渡览碉幅爱设兄押求拙潦曳尾纲强毫减抗织雁想哺押沤缺蛀膨蠕潜蛆韶锯蛹迈蹲皇奔七抠牢甚着炯惺秽遂启巢撩居休耽友苑贱近为诲鳃劫谩认韵爷该耿跪省吸棚咀道姐碧锹峭拌察避磁砷冰炭王良舟列辊一恫虑岂翔滋旭赚耶焚瞥取篆苯葵毖虐甄螟辗副耳椒持碱位架竭石妇靖骂涛周斩树跟Designation: D 6415 99e1Standard
2、 Test Method forMeasuring the Curved Beam Strength of a Fiber-ReinforcedPolymer-Matrix Composite1This standard is issued under the fixed designation D 6415; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision
3、. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1 NOTEEquation 5 was editorially corrected in December 2000.1. Scope1.1 This test method determines the curved beam strength ofa continuous
4、fiber-reinforced composite material using a 90 curved beam specimen (Fig. 1). The curved beam consists of two straight legs connected by a 90 bend with a 6.4-mm inner radius. An out-of-plane (through-the-thickness) tensile stress is produced in the curved region of the specimen when load is applied.
5、 This test method is limited to use with composites consisting of layers of fabric or layers of unidirectional fibers.1.2 This test method may also be used to measure the interlaminar tensile strength if a unidirectional specimen is used where the fibers run continuously along the legs and around th
6、e bend.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use.1.4
7、The values stated in SI units are to be regarded as standard. The values given in parentheses are provided for information purposes only.2. Referenced Documents2.1 ASTM Standards:D 883 Terminology Relating to Plastics2D 2734 Test Methods for Void Content of Reinforced Plas- tics3D 3171 Test Method f
8、or Fiber Content of Resin MatrixComposites by Matrix Digestion4D 3878 Terminology of High-Modulus Reinforcing Fibers and Their Composites4D 5229/D 5229M Test Method for Moisture Absorption Properties and Equilibrium Conditioning of Polymer Ma- trix Composite Materials41 This test method is under the
9、 jurisdiction of ASTM Committee D30 on Composite Materials and is the direct responsibility of D30.06 on Interlaminar Properties.Current edition approved May 10, 1999. Published July 1999.2 Annual Book of ASTM Standards, Vol 08.01.3 Annual Book of ASTM Standards, Vol 08.02.4 Annual Book of ASTM Stan
10、dards, Vol 15.03.FIG. 1 Test Specimen GeometryD 5687/D 5687M Guide for Preparation of Flat Composite Panels with Processing Guidelines for Specimen Prepara- tion4E 4 Practices for Force Verification of Testing Machines5E 6 Terminology Relating to Methods of Mechanical Test- ing5E 122 Practice for Ch
11、oice of Sample Size to Estimate aMeasure of Quality for a Lot or Process63. Terminology3.1 DefinitionsTerminology D 3878 defines terms relating to high-modulus fibers and their composites. Terminology D 883 defines terms relating to plastics. Terminology E 6 defines terms relating to mechanical test
12、ing. In the event of a conflict between terms, Terminology D 3878 shall have prece- dence over the other standards.3.2 Definitions of Terms Specific to This Standard:NOTE 1If the term represents a physical quantity, its analytical dimensions are stated immediately following the term (or letter symbo
13、l) in fundamental dimension form, using the following ASTM standard sym- bology for fundamental dimensions, shown within square brackets: M for mass, L for length, T for time, u for thermodynamic temperature, and nd for nondimensional quantities. Use of these symbols is restricted to analytical dime
14、nsions when used with square brackets, as the symbols may have other definitions when used without the brackets.5 Annual Book of ASTM Standards, Vol 03.01.6 Annual Book of ASTM Standards, Vol 14.02.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, Un
15、ited States.1D 6415 99e13.2.1 applied moment, M ML2T2, nthe moment applied to the curved test section of the specimen.3.2.2 curved beam strength, CBS ML1T2, nthe moment per unit width, M/w, applied to the curved test section which causes a sharp decrease in applied load or delamination(s) to form.3.
16、2.3 interlaminar tensile strength, F3u ML1T2, nthe strength of the composite material in the out-of-plane (through- the-thickness) direction.3.3 Symbols:3.3.1 CBS = curved beam strength (see 3.2.2).3.3.2 dx, dy = horizontal and vertical distances between two adjacent top and bottom loading bars, res
17、pectively.3.3.3 D = diameter of the cylindrical loading bars on the four-point-bending fixture.3.3.4 Er, Eu = moduli in the radial and tangential directions, respectively.3.3.5 F3u = interlaminar tensile strength (see 3.2.3).3.3.6 g = parameter used in strength calculation.3.3.7 lb = distance betwee
18、n the centerlines of the bottom loading bars on the four-point-bending fixture.3.3.8 l0 = distance along the specimens leg between the centerlines of a top and bottom loading bar.3.3.9 lt = distance between the centerlines of the top load- ing bars on the four-point-bending fixture.3.3.10 M = applie
19、d moment (see 3.2.1).3.3.11 P = total force applied to the four-point-bending fixture.3.3.12 Pmax = maximum force applied to the four-point- bending fixture before failure.3.3.13 Pb = force applied to the specimen by a single loading bar.3.3.14 r, u = cylindrical coordinates of any point in the curv
20、ed segment.3.3.15 ri, ro = inner and outer radii of curved segment.3.3.16 rm = radial position of the maximum interlaminar(radial) tensile stress.3.3.17 t = average thickness of specimen.3.3.18 w = width of the specimen.3.3.19 D = relative displacement between the top and bottom halves of the four-p
21、oint-bending fixture.3.3.20 k = parameter used in strength calculation.3.3.21 r = parameter used in strength calculation.3.3.22 f = angle from horizontal of the specimen legs in degrees.3.3.23 fi = angle from horizontal of the specimen legs at the start of the test in degrees (0.5 3 angle between th
22、e legs).3.3.24 sr = radial stress component in curved segment.4. Summary of Test Method4.1 A 90 curved-beam test specimen is used to measure the curved beam strength of a continuous-fiber-reinforced compos- ite material (Fig. 1). The curved beam strength represents the moment per unit width which ca
23、uses a delamination(s) to form.If the curved beam is unidirectional with all fibers running continuously along the legs and around the bend and an appropriate failure mode is observed, an interlaminar (through- the-thickness) tensile strength may also be calculated. The curved beam is uniform thickn
24、ess and consists of two straightlegs connected by a 90 bend with a 6.4-mm inner radius. The curved beam is loaded in four-point bending to apply a constant bending moment across the curved test section. An out-of-plane tensile stress is produced in the curved region of the specimen to cause the fail
25、ure.5. Significance and Use5.1 Out-of-plane stress analyses are not easily performed. Failure criteria are varied and poorly validated. Interlaminar allowables are not readily available. However, stress analysts routinely encounter structural details in which they cannot ignore the out-of-plane load
26、s. This test method is designed to produce out-of-plane structural failure data for structural de- sign and analysis, quality assurance, and research and devel- opment. For unidirectional specimens, this test method is designed to produce interlaminar tensile strength data. Factors that influence th
27、e curved beam strength and should therefore be reported include the following: material, methods of material preparation, methods of processing and specimen fabrication, specimen preparation, specimen conditioning, environment of testing, speed of testing, time at temperature, void content, and volu
28、me percent reinforcement.6. Interferences6.1 Failure in non-unidirectional specimens may be initiated from matrix cracks or free edge stresses. Consequently, the interlaminar strength calculated from non-unidirectional speci- mens may be in error.6.2 The stress state of a curved beam in four-point b
29、ending is complex. Circumferential tensile stresses are produced along the inner surface, and circumferential compressive stresses are produced on the outer surface. The radial tensile stress ranges from zero at the inner and outer surfaces to a peak in the middle third of the thickness. Consequentl
30、y, the failure should be carefully observed to ensure that a delamination(s) is producedacross the width before the failure data are used.6.3 Since stresses are nonuniform and the critical stress state occurs in a small region, the location of architectural charac- teristics of the specimen (for exa
31、mple, fabric weave, and tow intersections) may affect the curved beam strength.6.4 Nonlaminated, 3-D reinforced, or textile composites may fail by different mechanisms than laminates. The most critical damage may be in the form of matrix cracking or fiber failure, or both, rather than delaminations.
32、6.5 Material, Fabrication, and Specimen Preparation Poor material fabrication practices, lack of control of fiber alignment, and damage induced by improper coupon machin- ing are known causes of high material data scatter in compos- ites. The curved beam and interlaminar strengths measured using thi
33、s test method are extremely sensitive to fiber volume and void content. Consequently, the test results may reflect manufacturing quality as much as material properties.7. Apparatus7.1 Testing MachineThe testing machine shall be in conformance with Practices E 4, and shall satisfy the following requi
34、rements:7.1.1 Testing Machine HeadsThe testing machine shall have both an essentially stationary head and a movable head.2D 6415 99e17.1.2 Drive MechanismThe testing machine drive mecha-nism shall be capable of imparting to the movable head a controlled velocity with respect to the stationary head.
35、The velocity of the movable head shall be capable of being regulated in accordance with 11.6.7.1.3 Load IndicatorThe testing machine load-sensing device shall be capable of indicating the total load being carried by the test specimen. This device shall be essentially free from inertia lag at the spe
36、cified rate of testing and shall indicate the load with an accuracy over the load range(s) of interest of within 61 % of the indicated value.7.1.4 GripsEach head of the testing machine shall have a means to hold half of the four-point-bending fixture firmly in place. A convenient means of providing
37、an attachment point for each fixture half is through the use of a metal “T” in each grip. The lower part of the “T” is clamped in the grips, and the top part of the “T” provides a flat attachment surface for each fixture half.7.2 Four-Point-Bending FixtureA four-point-bending test apparatus as shown
38、 in Fig. 2 shall be used to load the specimen. Machine drawings for example fixtures are shown in the appendix. Other designs that perform the necessary functions are acceptable. The cylindrical loading bars shall have diam- eters. D, between 6 and 10 mm and be mounted on roller bearings. The horizo
39、ntal distance between the centers of the loading bars shall be 100 6 2 mm (lb) for the bottom fixture and 75 6 2 mm (lt) for the top fixture.7.3 Displacement IndicatorThe relative axial displace- ment between the upper and lower fixtures may be estimated as the crosshead travel provided the deformat
40、ion of the testing machine and support fixture is less than 2 % of the crosshead travel. If not, this displacement shall be obtained from a properly calibrated external gage or transducer located between the two fixtures. The displacement indicator shall indicate the displacement with an accuracy of
41、 61 % of the thickness of the specimen.7.4 Load Versus Displacement (P Versus D) RecordAnX-Y plotter, or similar device, shall be used to make aFIG. 2 Curved Beam in Four-Point Bendingpermanent record during the test of load versus displacement.Alternatively, the data may be stored digitally and pos
42、tpro- cessed.7.5 MicrometersThe micrometer(s) shall use a suitable- size diameter ball-interface on irregular surfaces such as the bag-side of a laminate, and a flat anvil interface on machined or very-smooth tooled surfaces. The accuracy of the instru- ments shall be suitable for reading to within
43、1 % of the sample width and thickness. For typical specimen geometries, an instrument with an accuracy of 625 m 60.001 in. is desirable for both thickness and width measurements.7.6 CalipersThe caliper(s) shall use a knife-edge inter- face on the curved surfaces of the specimen and a flat anvil inte
44、rface on machined or very-smooth tooled surfaces. The accuracy of the instruments shall be suitable for reading to within 1 % of the sample width and thickness. For typical specimen geometries, an instrument with an accuracy of 625m 60.001 in. is desirable for both thickness and width measurements.8
45、. Sampling and Test Specimens8.1 SamplingTest at least five specimens per condition unless valid results can be gained through the use of fewer specimens, such as the case of a designed experiment. For statistically significant data, the procedures outlined in PracticeE 122 should be consulted. Repo
46、rt the method of sampling.8.2 Specimen Lay-upThe laminate shall have a cross section of constant thickness. The thickness shall be in the range from 2 to 12 mm.8.2.1 Lay-up to Measure Curved Beam StrengthAny lay-up that can be manufactured to the specified dimensions may be used.8.2.2 Lay-up to Measure